When i install other editors they show up when I'm in the "Finder" and right click a file name (either directly, or under services). UltraEdit doesn't show up on either. Can i add this?

Apparently IDM has not (yet) added the information to the UEM to tell Finder that it is able to edit files of various types. In the meantime, one can choose a file, open the file info dialog, and set UEM as the default application for files of that type. I did this for *.txt and certain others that I wanted to always open in UEM by default. That works.

Also, one can drag the file to the UEM icon in the doc. That works also.